Electromagnetic pick up



March 17, 1931. p DQNLE ELECTROMAGNE TIC PICK-UP Filed Oct. 29, 1928 IN VEN TOR.

Patented Mar. l7, 1931 rmnonn r.

DONLE, or MERIDEN, connscrrcur, essrenoag BY Masha ASSIGNMENTS,

'ro RADIO INVENTIONS,'I1\TC., A coerce-Arron or NEW YORK ELECTROMAGNETIC PICK-UP Application filed October 29, 1928. Seria1 No. 315,803.

One object of my invention is to produce a simple but inexpensive form'of construction which will faithfully transform the mechanical impressions of the sound record into electric pulsations suitable for amplification and reproduction. A special object is to produce a device of this character which will afford a maximum amplitude of reproduction of the desired sound record with a minimum amplification of the needle scratch.

' In carrying out the invention I provide a Fig.1 is a front view of the principal parts of the apparatus. but omitting the casing which would ordinarily be employed with and stylus carrier.

such a device.

Fig. 2 is a sectional view on theplaneof:

the line 22 of Fig.- 1.' Fig. 3 is asectional-view on the plane cf the line 38 of Fig. 1.

'Fig. it is an exploded showing. the principal parts of the device...

. F ig; 5 is a perspective view of'thearmature The base 10 may be made of a die casting and provided with supportsfor the various elements including the permanent magnet 11,

- the magnet core members 12 and the combinedarmature and stylus carrier 13'. An extension 14 may also besecured to the face tofacilitateV-attachment to a movable tone arm or the like. Y t

vThe vmagnet 11 is suitably secured to the base as -for instance bythe screws 15 and the nuts 16. The feet ofthe L-shaped core memperspective a view bers 12 are clamped between the ends of the magnet and the base. 7 r The armature and stylus member is mad up of the armature proper 17, the stylus holder 18 and the spring 19. The stylus holder has a slotted extension 20 which isinterlocked with a slot 21 at the end offthe armature. The spring 19 is perforated and slipped over the end of the extension 20 and the-parts solderedorbrazed together.- The clamp 22 screws into the holder 18 to e'ngagethe stylus 23. The ends of the spring19-are soldered or otherwisesuitably, secured to the posts 24 which are formed integrally with the base and are'quite rigid. a

The cross piece 25 is supported onscrew studs 26 and 27 which are screwed into the bosses 28 in the base and anchored by set nuts 29. One end of the cross piece 25'is lield between two adjustable nuts 30 and 31 so that thatend of the cross piece'may be adjusted initially to the proper height. The other end of the cross piece 25is pressed intone direction byfthe spring 32 against the adjusting thumb piece 83 so that the cross piece may be forced towardthe base by the-screw and will be forced away 'fromthe base by'the'sprin g f whenthe screw is retracted. Asoft rubber damper 84 is interposed between the cross piece 25 and the forked end 35 of'the armature. f

A second damping member '36 also preferably formed of .softfrubber tubing is interposed between the armature andjthe'cross pieces37 directly over the'pole pieces of the magnet windings. The cross piece 37 issecured in place by screws 38'which screw into the upper end of the nut 16. p v

The. parts. are so designed and arranged that the principal part of the weight of. the pick-up is sustained by the stylus through the spring 19 sothattheparts are yieldingly'sup ported byv avspring capable of vibration. in

the direction of the axis of the stylus so that surface scratchinghas ,a minimum effect on the device. The armature is of course designed to vibrate in a direction axial to the poles of the magnet. This vibration is permitted by the twisting of the spring 19. Harmonic vibration tending to destroy the faithfulness of reproduction are prevented by the two damping members 34 and 36 which are offset from each other so as to bind upon the armature not only in its outer forked end but also at a point intermediate this end and thespring 19 which in efi'ect pivotally supports the armature. The parts are initially adjusted to produce the most eifective results but the position of the armature with respect to the pole pieces and the amount of damping may be readily adjusted by means of the check nuts 30 and 31 and the set screw 33. Normally the adjustment of the set screw 33 is sutficient and it is only intended that the nuts 30 and 31 shall be adjusted at the factory or in case of emer ency. The spring support 19 for the stylus and armature avoids the oh- 7 jectionable bearings with movable parts which are likely to wear and get out of adj ustment.

I claim:

1. An electro-magnetic pick-up comprising a supporting plate, a combined armature and stylus member, a spring supported by the plate and adapted to be vibrated torsionally and also toward and from a record surface, said armature and stylus member being carried by said spring,and anelectro-magnetic system electrically responsive to the vibrations which move the armature member laterally and produce torsion of said spring but unresponsive to movements of the armature and stylus member toward and from the record.

2. An electro-magnetic pick-up comprising a supporting plate, a spring supported by the plate and adapted to be vibrated torsionally and also toward and from a record surface, a combined armature and stylus member carried by said spring, an electro-magnetic system including a magnet having a coil electrically responsive to the lateral vibrations which move the armature and produce torsion of the spring, but unresponsive to movements of the armature toward and from the record, and damping means independent of the supporting spring for acting upon the armature and stylus member. l

3. An electro-magnetic pick-up comprising a base, a magnet having pole pieces secured j thereto, supporting posts arranged'near said pole pieces, a spring having its ends secured to said posts, an armature and stylusmember secured to said spring, damping means for the opposite end of said armature and damping means arranged between the first damping means and said spring.

4. An electro-magnetic pick-upcomprising a base having spaced posts at one edge'and a pair of screwthreaded studs near the center said pole piece.

5. An electromagnetic pick-up comprising a base having posts, an armature pivotally supported by said posts, an electro-magnet having a pole piece coacting with said armature, screw studs carried by said base,

a cross piece carried by said studs and adjustable thereon, a damping member arranged between said cross piece and one end of said armature, aspring on one of said studs pressing said cross piece in one direction and a thumb screw coacting. with said stud to move said cross piece in opposition to said spring.

6. An electro-magnetic pick-up comprising a base having spaced posts at one edge and a pair of screw threaded studs, an armature, a leaf spring having its center connected to said armature and its ends carried by said posts, a cross piece adjustably carried by said studs, a yielding damping member between said cross piece and said armature, means for adjusting said cross piece, an electro-magnet having a pole piece between said posts and said studs and coacting with said armature andv a damping member for said armature arranged opposite said pole piece and offset from the other damping member.

7. An electro-magnetic pick-up comprising a base, a 'magnet having pole pieces secured thereto, supporting posts arranged alongside of said pole pieces, a spring having its ends secured to said posts, an armature and stylus member secured to said spring, damping means for the opposite end of said armature and damping means arranged between the first damping means and said spring and a single screw for adjusting the damping action. v

8. An electro-magnetic pick' up comprising a base having a magnetic system including pole pieces, an armature and stylus supported by a leaf spring at one side of the pole pieces, said leaf spring being arranged to permit vibration of the stylus vertically adjustable damping means at the other side of the pole pieces and damping means arranged overthe pole pieces.

- 9. An electro-ma-gnetic pick-up compris ing a base having posts, a leaf spring carried thereby, an armaturepivotally supported by saidlspring,,an electro-magnet having a pole piececoacting with said armature,-studs carried by said base, a cross piece carried by said studs and adjustable thereon, a damping member arranged between. said cross piece and one end of said armature, a spring on one of said studspressing said cross piece in one direction and a thumbscrew coacting with said stud to move said cross piece inopposition to said spring.

10. An electro magnetio pick-up comprising a base, a magnet having pole pieces secured thereto, a spring supported by said base, an armature and stylus member secured 19 to said spring, damping means for the end of said member remote from said stylus and supplemental damping means arranged between: said first damping means and said spring, I both of said damping means being arranged 5 to act upon said integral member.

HAROLD P. DONLE. 

